Lubricating oil for refrigerator with compressor

ABSTRACT

Disclosed is a lubricating oil for compression-type refrigerator comprising, as a main component, a polyoxyalkyleneglycol derivative represented by the general formula: 
     
       
         R 1 [(OR 2 ) m OR 3 ] n   
       
     
     wherein symbols are as defined in the specification. Said lubricating oil has a favorable compatibility with refrigerants and an excellent lubricating property, and is utilized as the lubricating oil for compression-type refrigerator employing hydrogen-containing fluorocarbon compound refrigerants including R-134a or fluorocarbon compound refrigerants without hydrogen.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending Ser. No.07/502,872, filed Apr. 2, 1990, which is a continuation-in-part of Ser.No. 07/444,932, filed Dec. 4, 1989, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel lubricating oil forrefrigerators with a compressor. More particularly, it relates to alubricating oil for refrigerators with a compressor (compression-typerefrigerators), comprising as the main component a polyoxyalkyleneglycolderivative having a high lubricating property as well as a favorablecompatibility with hydrogen-containing fluorocarbon compounds such as1,1,1,2-tetrafluoroethane (hereinafter referred to as R-134a), which cansubstitute for Freon compounds such as dichlorodifluoromethane(hereinafter referred to as R-12) used as refrigerant and involved inenvironmental pollution problems.

2. Description of the Related Arts

Generally, a compression-type refrigerator is constituted of acompressor, a condenser, expansion bulbs, and an evaporator, having amechanism where the mixture of the refrigerant and the lubricating oilis circulating in a closed system. In such a refrigerator, though itdepends on the kind of apparatus, usually the temperature in thecompressor rises to 40° C. or more, while in the cooler, the temperaturecomes to be so low as −40° C. Accordingly, the refrigerant and thelubricating oil must circulate in the said system without phaseseparation in the said temperature range of −40° C. to +40° C. in mostcases.

If phase separation is caused while the running of the refrigerator, aseriously detrimental effect occurs affecting the life and efficiency ofthe apparatus. For example, if phase separation of the refrigerant andthe lubricating oil is caused in the compressor, moving parts becomeunderlubricated resulting in seizure or other troubles, which shortenthe life of the apparatus considerably. If phase separation is caused inthe evaporator, a lubricating oil having a high viscosity results, whichbrings lowering of efficiency in heat exchange.

Since a lubricating oil for refrigerators is used for the purpose oflubricating the moving parts of the refrigerator, its lubricatingability is regarded important as a matter of course. Particularly in thecompressor, the temperature becomes so high that a viscosity, sufficientto retain the oil film necessary for lubricating, is important.Necessary viscosity varies with the kinds or running conditions of thecompressor, but usually the preferable viscosity of the lubricating oilbefore blended with refrigerant is 2 to 250 cSt at 100° C. If theviscosity is lower than that range, the oil film becomes thinner therebycausing underlubricating and sealing properties become poor, while ifthe viscosity is higher than the above, the efficiency in heat exchangeis reduced. Since lubricating oils for refrigerator are used incirculation in a wide range of high to low temperatures, its viscosityindex is preferably high, and usually a viscosity index of 40 or more isrequired. Further, in addition to the above properties, a lowhygroscopicity to prevent the blocking of the bulb caused by icing atthe expansion bulb and other properties are required.

Heretofore, as the refrigerant for compression-type refrigerators, R-12has often been used, and as the lubricating oil, various mineral oilsand synthetic oils satisfying the required properties mentioned beforehave been used. R-12, however, has recently been restricted more andmore severely all over the world, for it is liable to causeenvironmental pollution including destruction of the ozonosphere.

In these circumstances, hydrogen-containing fluorocarbon compoundsincluding R-134a have attracted attention, as new refrigerants. Amongthe hydrogen-containing fluorocarbon compounds, R-134a especially hasonly a small possibility of destroying the ozonosphere, and cansubstitute for R-12, with little change in structure of the conventionalrefrigerators, and accordingly is favorable as a refrigerant forcompression-type refrigerators.

When the hydrogen-containing fluorocarbon compounds including saidR-134a are employed as the refrigerant for compression-typerefrigerators in place of R-12, the desirable lubricating oils come tobe those having high compatibility with the hydrogen-containingfluorocarbon compounds including R-134a, and also having highlubricating properties enough to satisfy the required propertiesmentioned above.

However, since the conventional lubricating oils which have been usedwith R-12 do not have a favorable compatibility with thehydrogen-containing fluorocarbon compounds including R-134a, a newlubricating oil suitable to these compounds consequently is required. Inthat case, particularly in the air-conditioner for automobiles, it isrequired that the construction of the mechanism be hardly changed on theoccasion of substituting for R-12. It is not desirable to change widelythe construction of the present mechanism because of lubricating oil.Accordingly, a lubricating oil having a very favorable compatibilitywith the hydrogen-containing fluorocarbon compounds, including R-134a,is required.

As lubricating oils having compatibility with R-134a, Ulcon LB-165 orUlcon LB-525 (Trade Mark, both produced by Union Carbide Co., Ltd.)composed of polyalkyleneglycol have been known, and it was reported thatthese lubricating oils are dissolved or compatible with R-134a in allproportions at a low temperature of −50° C. or lower (“ResearchDisclosure”, No. 17463 (October, 1978)). Moreover, a high viscosityrefrigerator oil composition of which the base oil ispoly-oxypropyleneglycolmonobutylether is known (Japanese PatentPublication No. 42119/1982). These lubricating oils arepolyalkyleneglycol derivatives having polypropylene glycol with ahydroxyl group at one of the terminals and a n-butyl ether bond (an-butoxy group) at the other terminal. They have a comparativelyfavorable compatibility with R-134a at low temperatures, but they do nothave sufficient compatibility with R-134a at high temperatures, and forexample, Ulcon LB-525 mentioned above is known to cause phase separationwith R-134a at room temperature (Specification of U.S. Pat. No.4,755,316).

On the other hand, a polyglycol having at least two hydroxyl groups in amolecule is proposed to be a favorable substance compatible with R-134a(Specification of U.S. Pat. No. 4,755,316).

In the said polyglycol, however, the.compatibility is not necessarysufficient.

Meanwhile, it is known that polyglycol generally shows a temperaturedependency that when the mixture with a fluorocarbon orchlorofluorocarbon compound is heated from a low temperature to a hightemperature, then the mixture phase-separated is once dissolved andphase-separated again.

On the other hand, R-134a and compounds which can dissolve it wereproposed for use in absorption-type refrigerators (Japanese Patent KokaiNo. 79175/1989). Said absorption-type refrigerators, however, are quitedifferent in mechanism from the before-mentioned compression-typerefrigerators, and tetraethylene-glycoldimethylether described in theExamples of the above-described Kokai is not proper as a lubricating oilfor compression-type refrigerators because of its particularly lowviscosity.

As described above, lubricating oil for compression-type refrigeratorshaving sufficiently favorable compatibility with R-134a as well as highlubricating properties have not been found yet, and their developmenthas been eagerly desired.

Replying to these requirements, the present inventors have earnestlystudied to develop a lubricating oil suitable to compression-typerefrigerators employing, as the refrigerant, hydrogen-containingfluorocarbon compounds including R-134a which are able to substitute forR-12 now involved in environmental pollution problems and otherfluorocarbon compounds which are difficult to decompose.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a lubricating oil forcompression-type refrigerators, having a favorable compatibility withhydrogen-containing fluorocarbon compounds including R-134a as therefrigerant.

Another object of the present invention is to provide a lubricating oilfor compression-type refrigerators, having a favorable compatibilitywith the above-described hydrogen-containing fluorocarbon compounds overthe whole temperature range of application.

A further object of the present invention is to provide a lubricatingoil for compression-type refrigerators, which has a favorablecompatibility and also a high lubricating properties as described above.

A still further object of the present invention is to provide alubricating oil for compression-type refrigerators, which has anexcellent anti-seizure property in addition to the above-describedproperties.

The present invention comprises the following Lubricating Oil I toLubricating Oil VII.

Lubricating Oil I

A lubricating oil for compression-type refrigerators, comprising, as themain component, at least one polyoxyalkyleneglycol derivativesrepresented by the general formula:

R¹—[—(OR²)_(m)—OR³]_(n)  (I)

wherein, R¹ indicates an alkyl group having 1 to 10 carbon atoms, anacyl group having 1 to 10 carbon atoms or an aliphatic hydrocarbon grouphaving 2 to 6 valencies, R² is an alkylene group having 2 to 4 carbonatoms, R³ is an alkyl group having 1 to 10 carbon atoms, or an acylgroup having 1 to 10 carbon atoms. n indicates an integer of 1 to 6, andm is an integer of 1 to 80.

Lubricating Oil II

A lubricating oil for compression-type refrigerators, comprising, as themain component, a polyoxyalkyleneglycol derivative represented by thegeneral formula:

R⁴(OR⁵)_(k)OH  (I)

wherein R⁴ indicates an alkyl group having 1 to 3 carbon atoms, R⁵indicates an alkylene group having 2 to 4 carbon atoms, and k indicatesa number of 6 to 80.

Lubricating Oil III

A lubricating oil for compression-type refrigerators, comprising, as themain component, polyoxyalkyleneglycol derivatives ofethyleneoxide-propyleneoxide copolymer represented by the generalformula:

R⁶—O—A—R⁷  (III)

and/or the general formula:

wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ indicate each a hydrogen or an alkylgroup having 1 to 3 carbon atoms, A is a polymerization chain ofethyleneoxide and propyleneoxide, consisting of p-times ethyleneoxideunits and q-times propyleneoxide units, and p and q are numberssatisfying the requirements:

0.1≦p/q=10, 5≦p+q≦100.

Lubricating Oil IV

A lubricating oil for compression-type refrigerators, characterized bycompounding a phosphate represented by the general formula:

wherein R¹⁶ indicates a hydrogen or an alkyl group having 1 to 3 carbonatoms, r indicates an integer of 1 or 2, when r is 2, R¹⁶s may beidentical or different and the total carbon number of (R¹⁶)_(r) is notmore than 3, with a base oil comprising, as the main component,polyoxyalkyleneglycol derivatives represented by the general formula:

R¹¹—O—A¹—R¹²  (VI)

and/or the general formula:

wherein R¹¹ to R¹⁵ indicate each a hydrogen or an alkyl group having 1to 3 carbon atoms, and A¹ to A³ indicate each polymerization chainsconsisting of 3 to 100 alkyleneoxide units of one kind or plural kinds,having 2 to 4 carbon atoms.

Lubricating Oil V

A lubricating oil for compression-type refrigerators, comprising, as themain component, polyoxyalkyleneglycol derivatives represented by thegeneral formula:

wherein R¹⁷, R¹⁸ and R¹⁹ indicate each an alkylene group having 2 to 4carbon atoms, and s, t and u indicate each an integer of 1 to 30, andhaving a viscosity at 40° C. of 50 to 250 cSt.

Lubricating Oil VI

A lubricating oil for compression-type refrigerator characterized bycontaining (a) polyoxyalkyleneglycol derivatives and (b) at least onecompound selected from the group consisting of (i) dibasic acid ester,(ii) fluorinated oil, (iii) polyhydric alcohol ester, and (iv) siliconefluoride.

Lubricating Oil VII

A lubricating oil for refrigerator with compressor containing as themain component a polyoxyalkyleneglycol derivative represented by thegeneral formula:

R⁴⁰—O—A—R⁴¹  (XIV)

wherein R⁴⁰ is an unsaturated hydrocarbon group having 2 to 10 carbonatoms (excluding aromatic hydrocarbon groups), A indicates apolymerization chain consisting of 3 to 90 alkyleneoxide units of one orplural kinds, having 2 to 4 carbon atoms, R⁴¹ is a hydrogen, an alkylgroup having 1 to 20 carbon atoms, an alkenyl group having 2 to 20carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an arylgroup having 6 to 20 carbon atoms, an aralkyl group having 7 to 20carbon atoms or a cycloalkyl group having 4 to 20 carbon atoms.Additional Lubricating Oils including Lubricating Oil VIII and IX willbe described hereinafter in greater detail.

DESCRIPTION OF PREFERRED EMBODIMENTS

First, Lubricating Oil I will be explained. Said Lubricating Oil Icomprises as the main component a polyoxyalkyleneglycol derivativerepresented by the general formula (I) as described before.

In the formula, R¹ is an alkyl group having 1 to 10 carbon atoms, anacyl group having 1 to 10 carbon atoms, or an aliphatic hydrocarbongroup having 2 to 6 valencies, R² is an alkylene group having 2 to 4carbon atoms, R³ is an alkyl group having 1 to 10 carbon atoms, or anacyl group having 1 to 10 carbon atoms, n is an integer of 1 to 6, and mis an integer of 1 to 80.

The alkyl group may be a straight chain alkyl group, branched chainalkyl group or cyclic alkyl group. Specific examples of these alkylgroups are a methyl group, an ethyl group, a n-propyl group, anisopropyl group, various butyl groups, various pentyl groups, varioushexyl groups, various heptyl group, various octyl groups, various nonylgroups, various decyl groups, a cyclopentyl group, a cyclohexyl groupand the like. If the carbon number of said alkyl group is in excess of10, the compatibility with R-134a is reduced, which causes phaseseparation. The preferable carbon number of alkyl groups is 1 to 6. Themost preferred lubricating oils of those represented by formula (I) arethose wherein the R¹ and R² groups are alkyl groups, especially methylgroups.

The alkyl group in the acyl group may be a straight chain-, a branchedchain-, or a cyclic alkyl group. Specific examples of the alkyl group inthe acyl group are a methyl group, an ethyl group, an n-propyl group, anisopropyl group, various butyl groups, various pentyl groups, varioushexyl groups, various heptyl groups, various octyl groups, various nonylgroups, a cyclopentyl group, a cyclohexyl group and the like.

If the carbon number of said acyl group is in excess of 10, thecompatibility with R-134a is reduced, which causes phase separation. Thepreferable carbon number of the acyl group is 2 to 6.

When said R¹ and R³ are each an alkyl group or an acyl group, R¹ and R³may be identical or different from each other.

Further, when n is 2 or more, plural R³ in one molecule may be identicalor different.

In case R¹ is an aliphatic hydrocarbon group having 1 to 10 carbon atomsand 2 to 6 valencies, said aliphatic hydrocarbon group may be a chain ora cyclic group. Examples of aliphatic hydrocarbon groups having twovalencies are an ethylene group, a propylene group, a butylene group, apentylene group, a hexylene group, a heptylene group, an octylene group,a nonylene group, a decylene group, a cyclopentylene group), and acyclohexylene group. Examples of aliphatic hydrocarbon group having 3 to6 valencies are residues resulting from removing a hydroxyl group frompolyhydric alcohols such as trimethylol propane, glycerol,pentaerithritol, sorbitol, 1,2,3-trihydroxycyclohexane, and1,3,5-trihydroxycyclohexane.

If the carbon number of said aliphatic hydrocarbon group is in excess of10, the compatibility with R-134a is reduced, which causes phaseseparation. The preferable carbon number is 2 to 6.

In the before-mentioned general formula (I), R² is an alkylene grouphaving 2 to 4 carbon atoms, and as the oxyalkylene group of therepeating unit, an oxyethylene group, an oxypropylene group, and anoxybutylene group are specified. Oxyalkylene groups in one molecule maybe identical or may vary in two or more kinds, but preferably at leastan oxypropylene unit is contained in one molecule.

In the general formula (I), n is an integer of 1 to 6, and definedaccording to the number of valencies of R¹. For example, when R¹ is analkyl group or an acyl group, n is 1. When R¹ is an aliphatichydrocarbon group having 2, 3, 4, 5 or 6 valencies, n comes to be 2, 3,4, 5 or 6, respectively. m is an integer of 1 to 80, and if m is beyondthe said range, the object of the present invention cannot attainedsufficiently.

The general formula (I) means not only one kind of polyoxyalkyleneglycolderivatives but also a mixture of two or more kinds of the derivatives.

The polyoxyalkyleneglycol derivatives represented by the general formula(I) used in the said Lubricating Oil I can be produced according tovarious methods shown below.

Method (A)

Alkyleneoxide having 2 to 4 carbon atoms including ethyleneoxide andpropyleneoxide are polymerized with water or alkali hydroxide as aninitiator, to obtain a polyoxyalkyleneglycol having hydroxyl groups atthe both terminals, represented by the general formula:

H—(OR²)_(a)—OH  (A₁)

wherein a is a number of which mean value is 6 to 80, and R² is asdefined before. Subsequently, both the hydroxyl groups of saidpolyoxyalkyleneglycol are etherified or esterified or one of thehydroxyl groups is etherificated and the other hydroxyl group isesterified to obtain a polyoxyalkyleneglycol derivative represented bythe general formula:

R—(OR²)_(a)—OR′  (A₂)

wherein R and R′ are each an alkyl group or an acyl group having 1 to 10carbon atoms, and they may be identical or different each other, and R²and a are as defined above.

Method (B)

Alkylene oxide having 2 to 4 carbon atoms is polymerized with monohydricalcohol having 1 to 10 carbon atoms or an alkali metal salt thereof asan initiator, to obtain a polyoxyalkyleneglycol monoalkyletherrepresented by the general formula:

R″—(OR²)_(a)—OH  (B₁)

wherein R″ is an alkyl group having 1 to 10 carbon atoms, and R² and aare as defined above, having an ether bond at one terminal and ahydroxyl group at the other terminal. Subsequently, the hydroxyl groupof the polyoxyalkyleneglycol monoalkylether is etherified or esterified,to obtain a polyoxyalkyleneglycol derivative represented by the generalformula:

R″—(OR²)_(a)—OR  (B₂)

wherein R² , R, R″ and a are as defined above.)

Method (C)

Alkyleneoxide having 2 to 4 carbon atoms is polymerized with polyhydricalcohol having 2 to 6 valencies, and having 1 to 10 carbon atoms oralkali metal salt thereof as an initiator, to obtain apolyoxyalkyleneglycol derivative having a hydroxyl group at oneterminal, represented by the general formula:

R″′—[—(OR²)_(b)—OH]_(c)  (C₁)

wherein R″′ is an aliphatic hydrocarbon group having 1 to 10 carbonatoms and 2 to 6 valencies, c is an integer of 2 to 6, and b is anumber, for which the mean value of b×c is 6 to 80, and R² is as definedabove. Subsequently, the hydroxyl group of the resultingpolyoxyalkyleneglycol derivative is etherified or esterified, to obtaina polyoxyalkyleneglycol derivative represented by the general formula:

R′″—[—(OR²)_(b)—OR]_(c)  (C₂)

wherein R², R, R″′, b and c are as defined above.

In these methods of production, in order to esterify the hydroxyl groupof the polyoxyalkyleneglycol having a hydroxyl group at its terminal orderivatives thereof, usually performed are a method to react saidsubstances with an aliphatic carboxylic acid having 1 to 10 carbon atomsor reactive derivatives such as acid anhydride, acid halide and esterthereof, or a method to convert the hydroxyl group of the saidpolyoxyalkyleneglycol or derivatives thereof to sulfonates or halides,which are reacted with said carboxylic acid or salt thereof.

Examples of said carboxylic acid are formic acid, acetic acid, propionicacid, butyric acid, valeric acid, caproic acid, caprylic acid, capricacid, cyclohexanecarboxylic acid and the like.

When esterification is effected by the use of said carboxylic acid oracid anhydride thereof or by transesterification using the ester of saidcarboxylic acid, acid catalysts such as sulfuric acid and p-toluenesulfonic acid are usually used. When esterification is effected with theuse of acid halides, usually amines are used as the dehydrohalogenatingagent.

On the other hand in order to etherify the hydroxyl group ofpolyoxyalkyleneglycol having a hydroxyl group at its terminal orderivatives thereof, usually performed are a method to react them withalkali metals such as metallic sodium or alkali metal salts of loweralcohol such as sodium methoxide, to obtain alkali metal salt of saidpolyoxyalkyleneglycol or derivative thereof, and then react alkyl halidehaving 1 to 10 carbon atoms or sulfonates, or a method to transform thehydroxyl group of said polyoxyalkyleneglycol or a derivative thereof tosulfonate or halide, and then react them with aliphatic alcohol having 1to 10 carbon atoms or alkali metal salts thereof.

In the polyoxyalkyleneglycol derivative thus obtained, the bonding styleof the oxyalkylene unit is usually a head-tail bond in case ofoxypropylene unit or oxybutylene unit, but head-head bonds and tail-tailbonds are also contained in some cases.

Lubricating Oil I of the present invention comprises, as the maincomponent, the polyoxyalkyleneglycol derivative thus obtained andrepresented by the general formula (I), and said polyoxyalkyleneglycolderivative may be used solely or two or more kinds of them may be usedin combination. Said lubricating oil can be favorably used even if itcontains, in addition to the before-mentioned polyoxyalkyleneglycolderivative represented by the aforementioned general formula (I), apolyoxyalkyleneglycol derivative having hydroxyl group(s) at itsterminals as long as the content of said hydroxyl groups is not morethan 30 mol % of the total terminal groups.

The object of the present invention cannot be attained withpolyoxyalkyleneglycol derivative wherein R¹ and R³ are aromatic groupsin the before-mentioned general formula (I), though the reason for thisis not clear.

Preferred are the polyoxyalkyleneglycol derivatives of the generalformula (I) wherein n is 1, and R¹ and R³ are methyl groups.

The reasons for this preference is that (1) polyoxyalkylene derivativeshaving a hydroxy group at the terminal of the molecule (one terminal orboth terminals) might cause the blocking of the expansion bulbs by icingsince the derivatives dissolve a relatively large amount of watertherein. (2) Accordingly, compounds having alkyl groups at bothterminals are preferred since they are free from blocking of expansionbulbs as heretofore described, among all compounds, those having methylgroups at both terminals are most preferred. The derivatives have ahighly favorable compatibility with the refrigerant R-134a.

Lubricating Oil I of the present invention is preferred to have aviscosity at 100° C. in the range of 2 to 50 cSt, more preferably 5 to30 cSt, much more preferably 6 cSt (n=1, m=12 in the general formula(I)) to 30 cSt, still more preferably 7 cSt (n=1, m=14) to 30 cSt, andmost preferably 9 cSt (n=1, m=19) to 30 cSt in order to retain thethickness of oil film necessary for lubricating and to maintainsufficient sealing properties. If necessary, to lubricating Oil I of thepresent invention can be added, various additives used in conventionallubricating oils such as anti-load additives, chlorine capturing agents,antioxidants, metal deactivating agents, defoaming agents, detergentdispersants, viscosity index improvers, oilness agents; antiwearadditives, extreme pressure agents, rust inhibitors, anti-corrosionagents, pour point depressants and the like.

The above-mentioned anti-load additives include organic sulfide-basedadditives such as monosulfides, polysulfides, sulfoxides, sulfones,thiosulfinates, sulfurized fats and oils, thiocarbonates, thiophenes,thiazols, methanesulfonic acid esters; phosphate-based additives such asphosphoric monoesters, phosphoric diesters and phosphoric triesters(tricresyl phosphate); phosphite-based additives such as phosphorousmonoesters, phosphorous diesters, and phosphorous triesters;thiophosphate-based additives such as thiophosphoric acid triesters;fatty acid-based additives such as higher fatty acid, hydroxyaryl fattyacids, carboxylic acid-containing polyhydric alcohol esters, and metalsoap; fatty acid ester-based additives such as polyhydric alcohol estersand acrylic acid esters; organic chlorine-based additives such aschlorinated hydrocarbons and chlorinated carboxylic acid derivatives;organic fluorine-based additives such as fluorinated aliphatic acids,ethylene fluoride resins, fluoroalkyl polysiloxanes and fluorinatedgraphite; alcohol-based additives such as higher alcohols; and metalliccompound-based additives such as naphthenates (lead naphthenate), fattyacid salts (fatty acid lead), thiophosphates (zincdialkyldithiophosphate), thiocarbamates, organomolybdenum compounds,organic tin compounds, organo-germanium compounds, and boric acidesters.

Chlorine capturing agents include compounds having glycidyl ether group,epoxyfatty acid monoesters, epoxy fats and oils and compounds having anepoxycycloalkyl group. Antioxidants include phenols(2,6-di-tert-butyl-cresol), aromatic amines (alpha-naphthylamine) andthe like. Metal deactivators include benzotriazole derivatives.Defoaming agents include silicone oil (dimethylpolysiloxane), andpolymethacrylates. Detergent dispersants include sulfonates, phenates,succinimides and the like.

Viscosity index improvers include polymethacrylate, polyisobutylene,ethylene-propylene copolymer, hydrogenated styrene-diene copolymer andthe like.

Lubricating Oil I of the present invention having a high compatibilitywith refrigerants as well as excellent lubricating ability is used forcompression-type refrigerators, and it is particularly suitable forcompression-type refrigerators employing R-134a as the refrigerant,since said lubricating oil has a good compatibility with R-134a, unlikethe conventional lubricating oils. Moreover, Lubricating Oil I can beused in mixture with another lubricating oil for compression-typerefrigerators, with the purpose of improving its compatibility withrefrigerants.

The description of the aforesaid Lubricating Oil II is as follows. ThisLubricating Oil II contains a polyoxyalkyleneglycol derivativerepresented by the general formula (II) as aforementioned as a maincomponent. Here in the formula, R⁴ is an alkyl group having 1 to 3carbon atoms, R⁵ is an alkylene group having 2 to 4 carbon atoms and kis a number of 6 to 80, preferably 10 to 40.

The alkyl group of this lubricating oil is any of a methyl group, anethyl group, a propyl group or an isopropyl group. If this alkyl grouphas 4 or more carbon atoms, compatibility with a hydrogen-containingfluorocarbon compound such as R-134a, etc. is reduced and phaseseparation comes to occur. Of these alkyl groups, a methyl group isparticularly preferred.

R⁵ in the aforesaid general formula (II) is an alkylene group having 2to 4 carbon atoms as heretofore described. Consequently, oxyalkylenegroups having a repeating unit represented by OR⁵ include an oxyethylenegroup, an oxypropylene group and an oxybutylene group. Oxyalkylenegroups in one molecule may be the same or two or more kinds ofoxyalkylene groups may be contained in one molecule. However, it ispreferred to contain at least one oxypropylene unit in one molecule. Analkylene group in an oxyalkylene group may be a straight-chain group orbranched group.

The k in the general formula (II) is a number of 6 to 80 on the average,preferably 10 to 40. If this average value is too small, lubrication isreduced, and if it is too large, solubility decreases, so the objects ofthe present invention cannot be satisfactorily attained.

The polyoxyalkyleneglycol derivative, which is represented by theaforesaid general formula (II), to be used as the lubricating oil of thepresent invention, can be produced, for example, by the followingmethods.

Method (D)

Polyoxyalkyleneglycol having hydroxyl groups at both terminalsrepresented by the general formula:

H(OR⁵)_(k)OH  (D₁)

wherein R⁵ and k are the same as the foregoing is obtained bypolymerizing alkylene oxide having 2 to 4 carbon atoms such as ethyleneoxide and propylene oxide, and water or alkali hydroxide as an initiatorand then a polyoxyalkyleneglycol derivative represented by the generalformula:

R⁴(OR⁵)_(k)OH  (II)

wherein R⁴, R⁵ and k are the same as the foregoing is obtained byetherifying one of the hydroxyl groups.

The etherification can be carried out by various methods, for example,the reaction of polyoxyalkyleneglycol with dialkyl sulfate, the reactionof alkoxide in polyoxyalkylene glycol with alkyl halide or the reactionof halogenated polyoxyalkyleneglycol wherein one terminal hydroxy groupis halogenated, with alkoxide, and the others.

The reaction of polyoxyalkyleneglycol with dialkyl sulfate is usuallycarried out in the presence of an aqueous alkali solution at atemperature of −10° C. to 100° C. for 5 minutes to 50 hours. When thereaction is carried out at a temperature of more than 40° C., one of twoalkyl groups contained in alkyl sulfate reacts, and at a temperature ofmore than 50° C., both alkyl groups react. If necessary, an inert liquidcan be used as a solvent. Dialkyl sulfates include dimethyl sulfate,diethyl sulfate, dipropyl sulfate and diisopropyl sulfate. Aqueousalkalis include sodium hydroxide, potassium hydroxide and the like.

The reaction of alkoxide in polyoxyalkyleneglycol with halogenated alkylis usually carried out at atmospheric pressure or under pressure at atemperature of 50° C. to 150° C. for 30 minutes to 30 hours. Solventssuch as toluene, tetrahydrofuran and the like can be used preferably.Halogenated alkyls include methyl chloride, methyl bromide, methyliodide, ethyl chloride, propyl chloride, isopropyl chloride and thelike.

The method in which one terminal hydroxyl group of polyoxyalkyleneglycolis reacted with alkoxide after halogenating is that derivative in whichhydroxy group at the terminal is halogenated, obtained by reactingpolyoxyalkylene glycol with halogenating reagents such as thionylchloride, phosphorus pentachloride, phosphorus pentabromide and the likeis reacted with alkoxide at a temperature of 50° C. to 150° C. for 30minutes to 30 hours. Alkoxides include sodium methoxide, potassiummethoxide, sodium ethoxide, sodium propoxide, sodium isopropoxide andthe like.

In the above Method (D), besides a polyoxyalkyleneglycol derivativewherein one terminal of polyoxyalkyleneglycol is alkylether and theother terminal thereof is a hydroxyl group, a polyoxyalkyleneglycolderivative and a polyoxyalkylene glycol material both terminals of whichare alkylethers are included. Polyoxyalkyleneglycol with alkylether atone of the terminals can be separated to be used. Also, it can be usedas a mixture without separating these components.

Method (E)

A polyoxyalkyleneglycol derivative represented by the general formula:

R⁴(OR⁵)_(k)OH  (II)

wherein R⁴, R⁵ and k are the same as the foregoing is obtained bypolymerizing alkylene oxide having 2 to 4 carbon atoms and monohydricalcohol having 1 to 3 carbon atoms or its alkali metal salt as aninitiator.

When alcohol is used as a material, aqueous alkali of 0.05 to 1.3equivalent to alcohol is used. Alcohol, and aqueous alkali or alkalimetal salt of alcohol are introduced in an autoclave and heated to atemperature of 50° C. to 150° C. The prescribed amount of alkylene oxideis introduced therein under pressure for 10 minutes to 50 hours whilestirring to obtain the desired polyoxyalkyleneglycol derivative.Monohydric alcohols include methanol, ethanol, propanol and isopropanol.Alkali metal salts of monohydric alcohol include sodium methoxide,potassium methoxide, sodium ethoxide, sodium isopropoxide and the like.

In the above Method (E), only a polyoxyalkyleneglycol derivative withalkylether at one terminal of the polyoxyalkyleneglycol and a hydroxylgroup at the other terminal thereof, is obtained. Therefore, Method (E)is preferable to Method (D) as the case may be.

A polyoxyalkyleneglycol derivative thus obtained may be used alone or ina mixture comprising two or more thereof.

The viscosity of Lubricating Oil II at 100° C. is preferably in therange of 2 to 50 cSt in order to maintain a thickness of oil filmsufficient to lubricate.

To Lubricating Oil II of the present invention, in the same way as inthe above Lubricating Oil I, various additives used in conventionallubricating oils can be added, if desired, for example, an anti-loadadditive, a chlorine capturing agent, an antioxidant, a metaldeactivator, a defoaming agent, a detergent dispersant, a viscosityindex improver, an oiliness agent, an anti-wear additive, an extremepressure agent, a rust preventative, a corrosion inhibitor, a pour pointdepressant and the like. Specific examples thereof are the same asdescribed before.

Subsequently, the detailed description of Lubricating Oil III in thepresent invention is as follows.

Lubricating Oil III contains a polyoxyalkyleneglycol derivativecomprising an ethylene oxide-propylene oxide copolymer represented bythe aforesaid general formula (III) and/or (IV) as a main component. R⁶,R⁷, R⁸, R⁹ and R¹⁰ indicate each a hydrogen or an alkyl group having 1to 3 carbon atoms (a methyl group, an ethyl group, an n-propyl group, ani-propyl group). Particularly, both R⁶ and R⁷, or R⁸, R⁹, and R¹⁰ arepreferably all alkyl groups, preferably methyl groups. A is a copolymerchain of p-times of ethylene oxide unit and q-times of propylene oxideunit and the form of the copolymer may be any of block copolymers,random copolymers, alternating copolymers and so on. p and q satisfy thefollowing requirements: 0.1≦p/q≦10, preferably 0.1≦p/q≦3, mostpreferably 0.2≦p/q≦2, and also 5≦p+q≦100, preferably 5≦p+q≦50. In thisway, a polyoxyalkyleneglycol derivative of the general formula (III)and/or (IV) to be used in Lubricating Oil III of the present inventionmust contain an ethylene oxide unit and a propylene oxide unit in thespecified proportion. If p/q is less than 0.1, there may occur theproblems that a viscosity index decreases and solubility also isreduced. If it exceeds 10, there are troubles that the product becomes awax state and solubility lowers. Further, if p+q is less than 5, thereis a problem that lubricity decreases because the viscosity is toosmall. If it exceeds 100, solubility and heat exchange efficiencydecrease undesirably.

Hereinafter, an ethylene oxide unit is referred to as EO, a propyleneoxide unit is referred to as PO and A is referred to as—(EO)_(m)—(PO)_(n)— to make understanding of the invention simple. Theseare not limited in a block copolymer but widely applied to a randomcopolymer, an alternating copolymer and the like.

Specific examples of a polyoxyalkyleneglycol derivative of the generalformula (III) or (IV) to be used in the present invention are:

 H₃C—O—(EO)₂₀—(PO)₂₀—CH₃,

H—O—(EO)₄—(PO)₁₄—CH₃,

H—O—(EO)₁₅—(PO)₁₅—H,

The above repeating unit numbers of EO and PO are shown only asexamples, and they can not be limited so far as the aforesaid conditionsare satisfied.

In Lubricating Oil III of the present invention, a polyoxyalkyleneglycolderivative of the above general formula (III) or (IV) may be used aloneor in a mixture comprising two or more thereof.

Lubricating Oil III of the present invention contains the abovepolyoxyalkyleneglycol derivative as a main component. In the same way asin the aforesaid Lubricating Oil I, various additives used inconventional lubricating oils, for example, an anti-load additive, achlorine capturing agent, an antioxidant, a metal deactivator, adefoaming agent, a detergent dispersant, a viscosity index improver, anoiliness agent, an anti-wear agent, an extreme pressure agent, a rustpreventative, a corrosion inhibitor, a pour point depressant and thelike, and further, a mineral oil and a synthetic oil used as a base oilfor a lubricating oil, can be added thereto, if desired. Specificexamples thereof are the same as aforementioned.

Further, the description of Lubricating Oil IV in the present inventionis as follows.

Lubricating Oil IV of the present invention contains apolyoxyalkyleneglycol derivative represented by the aforesaid generalformula (V) and/or (VI) as a main component. R¹¹, R¹², R¹³, R¹⁴ and R¹⁵indicate each a hydrogen or an alkyl group having 1 to 3 carbon atoms (amethyl group, an ethyl group, an n-propyl group, an iso-propyl group).Particularly, R¹¹ to R¹⁵ are preferably all alkyl groups, mostpreferably methyl groups. A¹ to A³ are (co)polymer chains comprising 3to 100 preferably 3 to 50 of one, two or more kinds of alkylene oxideunits having 2 to 4 carbon atoms. The numbers 3 to 100 representing theabove unit number indicate the mean value of polymerization numbers ofan alkylene oxide unit (an ethylene oxide-unit, a propylene oxide unit,a butylene oxide unit) and real numbers containing integers. That is,they are block copolymer chains, random copolymer chains or alternatingcopolymer chains containing d-times alkylene oxide units represented bythe general formula:

—(R^(d)O)—

wherein R^(d) is an alkylene group having 2 to 4 carbon atoms ande-times of alkylene oxide unit represented by the general formula:

—(R^(e)O)—

wherein R^(e) is an alkylene group having 2 to 4 carbon atoms, and d ande are each 0 to 100 satisfying the requirement d+e=3 to 100. When eitherd or e is 0, they become homopolymer chains of the other alkylene oxideunit.

If d+e exceeds 100, compatibility decreases to separate undesirably.

Specific examples of a polyoxyalkyleneglycol derivative represented bythe general formula (V) or (VI) to be used in the present invention are:

HO(C₃H₆O)_(4˜40)H

H₃CO(C₃H₆O)_(4˜40)CH₃

HO(C₃H₆O)₂ ₃₀—(C₂H₄O)_(2˜30)CH₃

H₃CO(C₃H₆O)_(2˜30)—(C₂H₄O)_(2˜30)CH₃

Copolymers referred to as the above block copolymerization contains notonly block copolymers but also random copolymers or alternatingcopolymers.

In Lubrication Oil IV of the present invention, a polyoxyalkyleneglycolderivative of the above formula (VI) or (VII) may be used alone or in amixture comprising two or more of both types.

In the present invention, phosphate represented by the aforesaid formula(V) is blended with a base oil containing a polyoxyalkyleneglycolderivative as a main component as described above. R¹⁶ as well as theaforesaid R¹¹ to R¹⁵ indicates hydrogen or an alkyl group having 1 to 3carbon atoms and r indicates an integer of 1 or 2. If two R¹⁶s arepresent, they may indicate different alkyl groups, but the total ofcarbon atoms in them must be 3 or less.

Specific examples of such phosphate represented by the general formula(V) are tricresol phosphate (TCP), triphenyl phosphate,tri-isopropylphenyl phosphate and so on. Of these, it is preferable touse tricresol phosphate.

In the present invention, the amount of the above phosphate to beblended is usually determined appropriately within the range of 0.1 to5% by weight, preferably 0.2 to 3% by weight based on the total amountof a refrigerating machine oil to be prepared.

In Lubricating Oil IV of the present invention, by combining apolyoxyalkyleneglycol derivative having the aforesaid structure and theabove phosphate, the effect of the phosphate as an anti-wear agent showssufficiently and also the anti-seizure property improves, bad influencessuch as deterioration of appearance and lowering of high criticaldissolution temperature decrease and, 'lubricity as a refrigeratingmachine oil improves.

Lubricating Oil IV of the present invention usually contains the abovepolyoxyalkyleneglycol derivative as a main component, whereto phosphateof the general formula (V) is blended. In addition, various additivesused in conventional lubricating oils, for example, an anti-loadadditive, a chlorine capturing agent, an antioxidant, a metaldeactivator, a defoaming agent, a detergent dispersant, a viscosityindex improver, an oiliness agent, an anti-wear additive, an extremepressure agent, a rust preventative, a corrosion inhibitor, a pour pointdepressant and the like can be blended.

And further, as a base oil besides the above polyoxyalkyleneglycolderivative, a mineral oil and a synthetic oil used as a base oil for alubricating oil can be added thereto, if desired. Specific examplesthereof are the same as described before.

Further, the description of Lubricating oil V in the present inventionis as follows.

This Lubricating Oil V is a compound obtained by adding alkylene oxideto glycerol, as shown in the general formula (VIII), wherein R¹⁷, R¹⁸and R¹⁹ may be the same alkylene groups or different alkylene groups.

Alkylene oxide added in the polyoxyalkyleneglycol derivative to be usedin the present invention, having 2 to 6 carbon atoms, such as ethyleneoxide, propylene oxide, butylene oxide and the like can be used.

In the formula, additional numbers s, t and u are integers of 1 to 30,preferably 2 to 15.

The polyoxyalkyleneglycol derivative of the general formula (VIII) canbe used as a mixture having the different additional number of moles.

The viscosity of the polyoxyalkyleneglycol derivative depends on thetype of an alkylene group and the additional number of moles (s, t, u).

A polyglycol compound to be used in the present invention needs to havea viscosity of 50 to 250 cSt, preferably 60 to 200 cSt at 40° C. If theviscosity is less than 50 cSt, the sealing property becomes inferior,and if it exceeds 250 cSt, the polyoxyalkyleneglycol derivative becomesinsoluble in a refrigerant.

According to the desired viscosity, the type and the average additionalnumber of moles can be determined.

Such polyoxyalkyleneglycol derivative obtained by adding propylene oxideor ethylene oxide to glycerol can be preferably used.

For example, a propylene oxide adduct of glycerol represented by theformula:

has a viscosity of 116 cSt at 40° C. A propylene oxide adduct ofglycerol represented by the formula:

has a viscosity of 103 cSt at 40° C. Both can be preferably used.

It is preferred that the purity of the polyoxyalkyleneglycol derivativeto be used in the present invention is 70% or more by weight.

In Lubricating Oil V of the present invention, a mineral oil or asynthetic oil can be blended to the above polyglycol compound to theamount of 50% or less by weight.

A mineral oil or a synthetic oil having a viscosity of 5 to 500 cSt at40° C. can be preferably blended. For example, (i) a paraffinic mineraloil, (ii) a naphthenic mineral oil, (iii) poly (Y-olefin, (iv)alkylbenzene, (v) alkyldiphenyl, (vi) ester (hindered ester, dibasicacid ester, polyolester, phosphate), (vii) polyglycol(polyphenyleneglycol, monofunctional- and difunctional-polyglycol) andthe like can be used. Of these, synthetic oils (iv) to (vii) having highsolubility in a refrigerant can be most preferably blended. If theviscosity of these mixed oils becomes less than 5 cSt, the amount of oilby circulation increases, losses due to evaporation become large and adisadvantage of poor sealing property occurs.

In Lubricating Oil V, it is preferred to maintain the water content at500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm orless and most preferably 100 ppm or less.

If the water content increases, rust is liable to form and further,solubility decreases. Though Lubricating Oil V is excellent in variousproperties as described above, it is relatively inferior in wearresistance to other Lubricating Oils, Lubricating Oils I to IV and VI.

In Lubricating Oil V of the present invention, additives to be addedusually, for example, an anti-wear agent, an antioxidant, a metaldeactivator, a chlorine capturing agent a defoaming agent and the otherscan be added appropriately, if desired.

Next, Lubricating Oil VI of the present invention will be explained. Insaid Lubricating Oil VI, polyoxyalkyleneglycol derivative used ascomponent (a) is not critical, but it is preferred to use at least onecompound selected from a compound represented by the general formula:

R²⁰—O—(R²¹O)_(w)R²²  (IX)

wherein R²⁰ and R²² are each a hydrogen, a hydrocarbon group or an acylgroup, and may be identical or different from each other, R²¹ is analkylene group having 2 to 6 carbon atoms, and w is a number of 2 ormore and a compound represented by the general formula:

wherein R²³, R²⁴ and R²⁵ are each an alkylene group having 2 to 6 carbonatoms, which may be identical or different from each other, R²⁶, R²⁷ andR²⁸ are each a hydrogen atom, a hydrocarbon group or an acyl group,which may be identical or different from each other, and x, y and z areeach a number of 2 or more, which may be identical or different fromeach other.

R²⁰ and R²² in the general formula (IX), R²⁶, R²⁷ and R²⁸ in the generalformula (X) are each a hydrogen atom, a hydrocarbon group or an acylgroup, and said hydrocarbon groups include an alkyl group, a cycloalkylgroup or an aryl group each having 1 to 30, preferably 1 to 12 carbonatoms. Examples of such hydrocarbon groups are a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, various butyl groups,various pentyl groups, various hexyl group, various heptyl groups,various octyl groups, various nonyl groups, various decyl groups,various undecyl groups, various dodecyl groups, various cyclopentylgroups, a cyclohexyl group, a methylcyclohexyl group, a phenyl group, atolyl group, a benzyl group, a phenethyl group and the like.

Acyl groups includes those groups derived from aliphatic carboxylicacids, alicyclic compounds, or aromatic carboxylic acids each having 1to 30, preferably 1 to 12 carbon atoms. Examples of such acyl groups arethose derived from carboxylic acids including formic acid, acetic acid,propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid,lauric acid, cyclohexane carboxylic acid, and benzoic acid.

R²¹ in the general formula (IX), R²³, R²⁴ and R²⁵ in the general formula(X) are each an alkylene group having 2 to 6 carbon atoms, preferably anethylene group, a propylene group, or a butylene group. Inpolyoxyalkyleneglycol derivative represented by the general formulas(IX) and (X), the oxyalkylene group as the repeating unit contained inone molecule may be identical or different.

R²⁰ and R²² in the general formula (IX) may be identical or differentfrom each other, but preferably either of them is a hydrocarbon group,more preferably an alkyl group. Specific examples of the polyglycolcompounds represented by said general formula (IX) are,

C₉H₁₉O(C₃H₆O)₁₀H

C₄H₉O(C₃H₆O)₁₈H

HO(C₃H₆O)₁₇H

R²³, R²⁴ and R²⁵ in the general formula (X) may be identical ordifferent from each other. R²⁶, R²⁷ and R²⁸ may be identical ordifferent from each other, but preferably all of them are hydrogenatoms. Furthermore, x, y and z may be identical or different from oneanother. A specific example of such a compound is:

Polyoxyalkyleneglycol derivative represented by the general formula (IX)or (X) can be produced according to a conventional process. For example,in a process for producing the polyoxyalkyleneglycol derivativerepresented by the general formula (IX), an alkyleneoxide having 2 to 6carbon atoms such as ethyleneoxide or propyleneoxide is polymerized withwater or alkali hydroxide as an initiator, to obtain a polyglycol havinghydroxyl groups at both terminals, and if one of or both the hydroxylgroups of the polyglycol thus obtained is/are etherified or esterifiedaccording to conventional processes, polyoxyalkyleneglycol derivativeshaving ether bond or ester bond at terminals can be obtained.

Further, if alkyleneoxide having 2 to 6 carbon atoms is polymerized withthe use of alcohols having the desired carbon number or phenols oralkali metal salts thereof as an initiator, polyoxyalkyleneglycolderivatives having an ether bond at one terminal and a hydroxyl group atthe other terminal can be obtained. And if the hydroxyl groups of saidderivative are etherified or esterified, a polyoxyalkyleneglycolderivative having ether bonds or ether bond and ester bond at both theterminals can be obtained.

In a process for producing polyoxyalkyleneglycol derivatives representedby the general formula (X), if an alkyleneoxide having 2 to 6 carbonatoms is polymerized with the use of glycerol or alkali metal saltsthereof as an initiator, a polyglycolether of glycerol having threehydroxyl groups at the terminals can be obtained, and if the hydroxylgroups of the said polyglycolether are etherified or esterifiedaccording to a conventional process, a polyglycol ether(polyoxyalkyleneglycol derivative) of glycerol having ether bonds orester bonds at the terminals can be obtained.

In Lubricating Oil VI in the present invention, one of theabove-mentioned component (a) may be used solely, or two or more kindsmay be used in combination.

In Lubricating Oil VI of the present invention, at least one compoundselected from the group consisting of (i) dibasic acid ester, (ii)fluorinated oil (iii) polyhydric alcohol ester, and (iv) fluorosiliconeis used as component (b).

As the dibasic acid ester of component (i), for example, a compoundrepresented by the general formula:

R²⁹OOC—A⁴—COOR³⁰  (XI)

wherein R²⁹ and R³⁰ are each an alkyl group, a cycloalkyl group or anaryl group each having 1 to 20 carbon atoms and may be identical ordifferent from each other, and A⁴ is an alkylene group, a cycloalkylenegroup or a phenylene group, is used. Typical examples of such dibasicacid esters are di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate,cyclohexane-1,4-dicarboxylic acid di-2-ethylhexyl, diisodecyl phthalateand the like.

A preferred example of the fluorinated oil as component (ii) ismonochlorotrifluoroethylene polymer represented by the general formula:

wherein X and X are each a halogen atom, and may be identical ordifferent from each other, and j is a number, for which averagemolecular weight is 250 to 1500. As the said monochlorotrifluoroethylenepolymer, Daifloil 10 and Daifloil 20 (Trade Mark, both produced byDaikin Industry Co., Ltd.) are commercially distributed.

Preferable examples of polyalcoholester as component (iii) aremonovalent or divalent aliphatic esters of polyhydric alcohols such asneopentyl glycol, glycerol, trimethylol ethane, trimethylol propane,pentaerithritol, and sorbitol.

Typical examples of such polyhydric alcohol esters are trimethylolpropane caproic acid ester, pentaerithritol propionic acid ester,pentaerithritol caproic acid ester, trimethylol prouane adipic acidester and the like.

An Example of fluorosilicone as component (iv) is a compound representedby the general formula:

wherein at least one of R³¹, R³², R³³, R³⁴, R³⁵ and R³⁶ is afluorohydrocarbon group having 1 to 30 carbon atoms, and others arehydrocarbon groups, acyl groups, alkoxyl groups or fluorohydrocarbongroups each having 1 to 30 carbon atoms, and may be identical ofdifferent from one another, and v is 0 or an integer of 1 or more.

The hydrocarbon group in the fluorosilicone represented by the generalformula (XIII) is an alkyl group, a cycloalkyl group or an aryl group,and in the fluorohydrocarbon group, at least one hydrogen atom of thesehydrocarbon groups is substituted by a fluorine atom.

Further, in said alkoxyl group and acyl group, when oxygen atom orcarbonyl group is removed, the residues comprise an alkyl group, acycloalkyl group or an aryl group. Typical example of such afluorosilicone is LS-8210 (Trade Mark, produced by Shin-etsu ChemicalIndustry Co., Ltd.), which is commercially available.

In Lubricating Oil VI of the present invention, at least one compoundselected from the group consisting of component (i), component (ii),component (iii) and component (iv) is compounded as component (b) withcomponent (a). The amount of said component (b) is defined usually inthe range of 0.01 to 50% by weight, particularly in the range of 0.1 to30% by weight of the total amount of component (a) and component (b). Ifthe amount is less than 0.01% by weight, the effect of improvingsolubility at high temperatures to fluoroalkanes as refrigerant is notshown sufficiently, and if it is in excess of 50% by weight, stabilityor blend stability will be reduced.

Lubricating Oil VI of the present invention can be added with variousadditives which are conventionally used for refrigerator oils, as longas the object of the present invention might not be hindered. Examplesof such additives are anti-wear agents, antioxidants, metaldeactivators, chlorine capturing agents, defoaming-agents, pour pointdepressants, viscosity index improvers and the like.

The lubricating oils of the present invention are excellent incompatibility with refrigerants and in lubricating property, andaccordingly utilized as lubricating oils for various refrigeratingmachines using fluoroalkane (flon) refrigerant, including acompression-type refrigerators. Particularly, unlike the conventionallubricating oils, the lubricating oil in the present invention has goodcompatibility with hydrogen-containing fluorocarbon compounds(hydrogen-containing fluoroalkane) such as R-134a and the like, forexample, 1,1,2,2tetrafluoroethane (R-134),1,1-dichloro-2,2,2trifluoroethane (R-123), 1-chloro-1,1-difluoroethane(R-142b), 1,1-difluoroethane (R-152a), chlorodifluoromethane (R-22),trifluoromethane (R-23). This solubility is satisfactory throughout thewhole temperature range.

Consequently, the lubricating oil in the present invention can beexpected to be effectively used as a lubricating oil for refrigeratorsusing various hydrogen-containing fluorocarbon compounds as arefrigerant, a cooler (particularly car air-conditioner), a heat pumpand the like. Also, this lubricating oil can be used by mixing withother lubricating oils for compression-type refrigerators.

An explanation of the Lubricant Oil VII which polyoxyalkyleneglycolderivative represented by the general formula (XIV) is as follows:

Herein R⁴⁰ is an unsaturated hydrocarbon group having 2 to 10 carbonatoms excluding aromatic unsaturated hydrocarbons, such as an alkenylgroup, an alkynyl group, a cycloakenyl group, more specifically a vinylgroup, an allyl group, an isopropenyl group, a butenyl group, ethynylgroup, propynyl group and butynyl group.

R⁴¹ is as described before, a hydrogen, an alkyl group having 1 to 20carbon atoms (including a methyl group, an ethyl group, a propyl group,and butyl group), an alkenyl group having 2 to 20 carbon atoms(including a vinyl group, an allyl group, and a butenyl group), analkynyl group having 2 to 20 carbon atoms (including an ethynyl group,and propynyl group), an aryl group having 6 to 20 carbon atoms(including a phenyl group, a tolyl group, a xylyl group, a nonylphenylgroup, and a dodecylphenyl group, an aralkyl group having 7 to 20 carbonatoms (including a benzyl group and a phenethyl group) or a cycloalkylgroup having 4 to 20 carbon atoms (including a cyclohexyl group, acycloheptyl group, a methylcyclohexyl group, and a nonylcyclohexylgroup). Among them, preferred are a hydrogen, an alkyl group having 1 to4 carbon atoms and an alkenyl group having 2 to 4 carbon atoms.

A is a (co)polymerization chain consisting of 3 to 90-times, preferably3 to 50-times alkyleneoxide units of one or plural kinds, having 2 to 4carbon atoms. Therein, the numbers 3 to 90 representing the above unitnumber indicates the mean value of the polymerization degree ofalkyleneoxide unit (an ethyleneoxide unit, a propyleneoxide unit, abutyleneoxide unit), showing real numbers including integers.

That is, A is a block copolymerization chain, a random copolymerizationchain, or an alternating copolymerization chain containing a-timesalkyleneoxide units represented by the general formula:

—(R⁴²O)—

wherein R⁴² indicates an alkylene group having 2 to 4 carbon atoms andb-times alkyleneoxide units represented by the general formula:

—(R^(42′)—O)—

wherein R^(42′) is an alkylene group having 2 to 4 carbon atoms, and aand b are each a number of 0 to 90, satisfying the requirement: a+b=3 to90. In case either of a and b is 0, the polymer chain becomes ahomopolymerization of another alkyleneoxide unit.

Herein, if a+b exceeds 90, compatibility with a refrigerant decreases tocause two-layer separation undesirably.

Examples of polyoxyalkyleneglycol derivatives represented by the generalformula (XIV) mentioned above are:

CH₂═CH—CH₂O(C₃H₆O)_(4˜40)H

CH₂═CH—CH₂O(C₃H₆O)_(4˜40)CH₃

CH₂═CH—CH₂O(C₃H₆O)_(4˜40)—CH₂CH═CH₂

CH₂═CH—CH₂O(C₃H₆O)_(2˜20)—(C₂H₄O)₂ ₂₀—CH₃

CH₂CHO(C₃H₆O)_(4˜40)H

CH₂═CHO(C₃H₆O)_(4˜40)CH═CH₂

CH₂═CHO(C₃H₆O)_(4˜40)CH₃

CH═CO(X₃H₆O)_(4˜40)H

CH═CO(C₃H₆O)_(4˜40)C≡CH

(copolymers shown by the above block copolymerization includes not onlyblock copolymers but also random copolymers or alternating copolymers.)

Lubricating oil VIII of the invention comprises components (A) and (B)as the main components, wherein component (A) is polyoxypropyleneglycoldimethylether having a kinematic viscosity of 2 to 50 cSt, preferably 5to 30 cSt at 100° C., and specifically represented by the formula:

CH₃O(C₃H₆O)_(m)CH₃  XV

wherein m indicates the degree of polymerization and component (B) is acompound represented by the general formula:

CH₃O(C₂H₄O)_(x)(RO)_(y)CH₃

wherein R indicates a propylene group or butylene group, x and yindicate real numbers satisfying the requirements:

0.01<44x/M

in which M is the molecular weight of the compound represented by theabove formula and

5≦x+y≦100;

however, when x is a plural number, Rs may be identical to or differentfrom each other, in such a ratio that the content of ethylene oxide unit(C₂H₄O) may be 1 to 30% by weight based on the total weight of (A) and(B).

In the above formula XV, both the terminals must be methyl groups. Ifeither or both of the terminals are ethyl groups and the like, saidlubricating oil becomes poor in compatibility with R-134a. However,polyoxypropyleneglycol monomethylether, polypropyleneglycol and the likecan be contained, provided that it is in a small amount of 30% by weightor less based on the total amount of component (A).

Component (B) of Lubricating Oil VIII of the invention is, as describedabove, a compound represented by the general formula XVI:

CH₃O(C₂H₄O)_(x)(RO)_(y)CH₃  XVI.

Representative compounds are polyoxyethylene polyoxypropyleneglycoldimethylether, polyoxyethylene polyoxybutyleneglycol dimethylether, orpolyoxyethylene polyoxypropylene polyoxybutyleneglycol dimethylether ormixtures thereof. In the general formula XVI, R indicates anoxypropylene group (or propylene oxide group) (C₃H₆O) or an oxybutylenegroup (or butylene oxide group) (C₄H₈O), or a mixture thereof; x and yare real numbers satisfying 0.01<44x/M (M is the molecular weight of thecompound represented by the above formula XVI), and 5≦x+y≦100. Morespecifically, x and y satisfy the requirements: 1≦x≦100, 0≦y≦99 and0.1≦x/(x+y)≦1. The most preferred x and y are those which satisfy therequirements: 10≦x+y≦50 and 0.2≦x/(x+y)≦1.

Satisfying the equation 0.01<44x/M means that the content ofethyleneoxide unit (C₂H₄O) exceeds 0.01 (ratio by weight) of thecompound represented by the general formula XVI. If the value of 44x/Mis 0.01 or less, the content of the ethylene oxide unit in the mixturedoes not reach the prescribed value, to lead to an insufficient antiwearproperty.

Also in component (B), both the terminals of the molecule should bemethyl groups (that means dimethylether) like component (A). If eitherone or both of the terminals are ethyl groups, propyl groups and thelike, the compatibility with R-134a becomes low. In the general formulaXVI, a block polymer is shown for convenience, but actually it is notlimited to block polymer, but may be random polymer, alternating polymeror graft polymer. In other words, the ethyleneoxide group andpropyleneoxide group or butyleneoxide group may be bonded in any ofvarious forms.

In lubricating Oil VIII of the invention, the above mentioned component(B) is compounded so that the content of ethyleneoxide unit (C₂H₄O) maybe 1 to 30% by weight, preferably 3 to 20% by weight of the totalamount. If it is less than 1% by weight, the resulting oil becomesinsufficient in antiwear property. If it is in excess of 30% by weight,troubles are caused in suitability to sealing materials, anti-peelingproperties for coating material is lowered, and hygroscopicity increasesundesirably. In addition, Lubricating Oil VIII loses its compatibilitywith fluorocarbon refrigerant containing no hydrogen such as R-12.Particularly, when the kinematic viscosity is high, the compatibilityfalls largely.

On the other hand, Lubricating Oil IX of the invention comprises maincomponent (C) which is a compound having a kinematic viscosity at 100°C. of 2 to 50 cSt and is represented by the general formula XVII:

CH₃O(C₂H₄O)_(z)(RO)_(w)CH₃  XVII

wherein R indicates a propylene group or a butylene group, z and w arereal numbers satisfying the requirements:

0.01≦44z/M′≦0.3

in which M′ is the molecular weight of the compound represented by theabove formula and

5≦z+w≦100.

However, when w is a plural number, Rs may be identical to or differentfrom each other. The main component (C) preferably has a kinematicviscosity of 5 to 30 cSt at 100° C. Representative compounds representedby the general formula XVII include polyoxyethylenepolyoxypropyleneglycol dimethylether, polyoxyethylenepolyoxybutyleneglycol dimethylether, or polyoxyethylene polyoxypropylenepolyoxybutyleneglycol dimethylether. Said component (C) is basicallyidentical to the above-mentioned component (B), but the content ofethyleneoxide unit (C₂H₄O), that is, 44z/M, of component (C) must be0.01 to 0.3, preferably 0.03 to 0.2.

In Lubricating Oil VIII of the invention, the proportion of theabove-mentioned ethyleneoxide unit is controlled to be in the range of 1to 30% by weight by compounding components (A) and (B), while inLubricating Oil IX, the proportion of the ethyleneoxide unit iscontrolled in the prescribed range by the amount of the above-mentionedcomponent (C).

Lubricating Oil VIII of the invention comprises the above-mentionedcomponents (A) and (B) as the main components (or essential components),and Lubricating Oil IX comprises component (C) as the main component.Furthermore, various additives are used in the conventional lubricatingoils, such as anti-load additives including extreme-pressure agents,antiwear agents, antioxidants, metal deactivating agents, defoamingagents, detergent dispersants, viscosity index improvers, rustinhibitors, anti-corrosion agents, pour point depressants, and further,mineral oils and synthetic oils to be used as the base oil forlubricating oils can be added, if necessary.

The present invention is described in greater detail with reference tothe following examples.

PREPARATION EXAMPLE 1

In a 200-milliliter three-necked glass flask equipped with a stirrer anddropping funnel, 50 g of Unilube MB-11 (polyoxypropyleneglycolmono-n-butylether, average molecular weight: 1000) produced by NipponOil & Fats Co., Ltd., 9.5 g (0.12 mol) of pyridine and 100 ml of ethylether were placed and then, 9.4 g (0.12 mol) of acetyl chloride wasadded through a dropping funnel over 30 minutes, while stirring at roomtemperature. After heating and refluxing for 2 hours, the reactionmixture was cooled to room temperature, was transferred into aseparating funnel and was washed five times with 50 ml of saturatedbrine each time. After the ether was distilled away, the residue wasdried at 100° C. for one hour at a reduced pressure with a vacuum pumpto obtain 49.0 g of the desired acetate of Unilube MB-11.

PREPARATION EXAMPLE 2

In a 300-milliliter three-necked glass flask equipped with a stirrer anda distillation head, 75 g of Unilube MB-11 produced by Nippon Oil & FatsCo., Ltd., and 50 ml of toluene were placed, and 20 ml of toluene wasdistilled away to remove water content, while heating and stirring. Thenthe distillation head was taken off, a cooler and a dropping funnel wereattached, and thereafter 11.9 g (0.15 mol) of pyridine and 50 ml oftoluene were added. While stirred at room temperature, 16.0 g (0.15 mol)of n-butyryl chloride was added through a dropping funnel over 30minutes. After heating and refluxing for 4 hours, the reaction mixturewas cooled to room temperature, was poured into a separating funnel andwas washed five times with 50 ml of saturated brine each time. Aftertoluene was distilled away, the residue was dried at 100° C. for onehour at a reduced pressure with a vacuum pump to obtain 70.5 g of thedesired n-butyric acid ester of Unilube MB-11.

PREPARATION EXAMPLE 3

The same procedure was repeated as in Preparation Example 2 except that16.0 g (0.15 mol) of isobutyryl chloride was used in place of n-butyrylchloride to obtain 74 g of isobutyric acid ester of Unilube MB-11.

REFERENCE EXAMPLE 1

The same procedure was repeated as in Preparation Example 1 except that16.9 g (0.12 mol) of benzoyl chloride was used in place of acetylchloride to obtain 57.0 g of benzoate of Unilube MB-11.

REFERENCE EXAMPLE 2

in a 200-milliliter three-necked glass flask equipped with a stirrer anda dropping funnel, 50 g of Unilube MB-11 produced by Nippon oil & FatsCo., Ltd., 7.9 g (0.14 mol) of potassium hydroxide and 80 ml of toluenewere placed, and then, 15.2 g mol) of benzyl chloride was added througha dropping funnel over 30 minutes, while heating and refluxing tolueneand stirring. Then the mixture was heated and refluxed for 4 hours,cooled to room temperature, and the reaction mixture was poured into aseparating funnel and was washed five times with 50 ml of saturatedbrine each time. After toluene was distilled away, the residue was driedat 100° C. for one hour at a reduced pressure (0.1 MmHg) with a vacuumpump to obtain 49.0 g of the desired benzyl ether of Unilube MB-11.

PREPARATION EXAMPLE 4

In a 300-milliliter three-necked glass flask equipped with a stirrer anda distillation head, 65 g of polyoxypropyleneglycol mono-n-butylether(average molecular weight, 1120) and 70 ml of toluene were placed, andabout 20 mi of toluene was distilled away to remove water content, whileheating and stirring. After cooling, 25 g (0.13 mol) of methanolsolution of sodium methoxide (28% by weight) was added and heated todistill away methanol and about 20 mi of toluene. After cooling, thedistillation head was taken off, and a cooler and a dropping funnel wereattached. Then 30 g (0.19 mol) of ethyl iodide was added through adropping funnel over 30 minutes, while heating at 50° C. and stirring.After heating and stirring at 50° C. for one hour, at 70° C. for 3 hoursand a 105° C. for 1.5 hours, the mixture was cooled to room temperature.Then, the reaction mixture was poured into a separating funnel and waswashed five times with 50 ml of saturated brine each time. After toluenewas distilled away, the residue was dried at 100° C. for one hour at areduced pressure with a vacuum pump to obtain 58 g of the desiredethylether derivative of polyoxypropyleneglycol mono-n-butylether.

PREPARATION EXAMPLE 5

The same procedure was repeated, as in Preparation Example 4 except that65 g of polyoxypropyleneglycol (average molecular weight: 1100) having ahydroxyl group at each of both terminals was used in place ofpolyoxypropyleneglycol mono-n-butylether, and 50 g (0.27-mol) of ethanolsolution of sodium methoxide (28% by weight) and 60 g (0.38 mol) ofethyl iodide were used to obtain 62 g of the desiredpolyoxypropyleneglycol ether.

PREPARATION EXAMPLE 6

The same procedure was repeated as in Preparation Example 4 except that65 g of polyoxypropyleneglycol (average molecular weight: 1000)derivative having three hydroxyl groups in a molecule obtained bypolymerizing propylene oxide using a glycerol as an initiator in placeof polyoxypropyleneglycol mono-n-butylether was used, and 50 g (0.26mol) of methanol solution of sodium methoxide (28% by weight) and 90 g(0.58 mol) of ethyl iodide were used to obtain 61 g of the desiredpolyoxypropyleneglycol triethylether derivative.

PREPARATION EXAMPLE 7

In a 300-milliliter three-necked glass flask equipped with a stirrer anda distillation head, 50 g of Sannix PP-1000 (polyoxypropyleneglycolhaving a hydroxyl group at each of both terminals, average molecularweight: 1000) produced by Sanyo Chemical Industries, Ltd. and 80 ml oftoluene were placed, about 20 ml of toluene was distilled away to removewater content, while heating and stirring.

After cooling, 25 g (0.13 mol) of methanol solution of sodium methoxide(28% by weight) was added, and the mixture was heated to distill awaymethanol and about 20 ml of toluene.

After cooling, the content was poured into a 300 milliliter stainlesssteel autoclave equipped with a stirrer, and 36.8 g (0.26 mol) of methyliodide was added and sealed. Then, the mixture was heated at 50° C. to70° C. over 4.5 hours and reacted at 85° C. for 4 hours. After coolingto room temperature, the reaction mixture was dissolved in the mixtureof 100 ml of water and 200 ml of methanol, and was passed through a 200ml column of cation-exchange resin, and then through a 200 ml column ofanion-exchange resin.

After the solvent was distilled away, the residue was dried for one hourat a reduced pressure (0.1 MmHg) with a vacuum pump to obtain 42.5 g ofthe desired dimethyl ether derivative of Sannix PP-1000. In thederivative, the infrared absorption spectrum (3450 cm⁻¹) ascribable to ahydroxyl group was lost.

PREPARATION EXAMPLE 8

The same procedure was repeated as in Preparation Example 7 except that60 g of Nissan Uniol D-1200 (polyoxypropyleneglycol having a hydroxylgroup at each of both terminals, average molecular weight: 1200)produced by Nippon Oil & Fats Co., Ltd. was used in place of SannixPP-1000 to obtain 49 g of dimethylether derivative of Nissan UniolD-1200. In the derivative, the infrared absorption spectrum (3450 cm⁻¹)ascribable to a.hydroxyl group was lost.

EXAMPLES 1 to 8, COMPARATIVE EXAMPLES 1 to 4

The compatibility with R-134a of the compounds obtained in PreparationExamples 1 to 8, Reference Examples 1 to 2, and polyglycol as thestarting material of Preparation Examples 1 and 4 was measured.

A specified sample was added into a pressure glass ampule so that theamount of the sample would be 10% by weight or 20% by weight to R-134a(1,1,1,2-tetrafluoroethane), and this was jointed to a vacuum pipe andR-134a gas pipe. Afterwards, the ampule was subjected to vacuumdegassing at a room temperature, and cooled with liquid nitrogen to takeout the specified R-134a. Then, the ampule was sealed, heated from −40°C. in a thermostat and the starting temperature of phase separation wasmeasured. The higher phase separation temperature is preferable. Theresults were shown in Table 1.

TABLE 1 Starting Temperature of Phase Separation (° C.) Ratio ofpolyglycol to 1,1,1,2-tetrafluoroethane Viscosity (cSt) Viscosity (wt %)No. Sample From 40° C. 100° C. Index 10% 20% Example 1 Acetate ofUnilube MB-11 Product of 48.23 9.77 194 71.0 74.0 Preparation Example 1Example 2 n-butyrate of Unilube MB-11 Product of 46.72 9.96 207 66.566.5 Preparation Example 2 Example 3 Isobutyrate of Unilube MB-11Product of 45.44 9.61 203 66.5 67.0 Preparation Example 3 ComparativeUnilube MB-11 Material of 56.10 10.8 187 51.5 54.0 Example 1 PreparationExample 1 Comparative Benzoate of Unilube MB-11 Product of 72.03 12.58175 15.0 −3.0 Example 2 Reference Example 1 Comparative Benzyl ether ofUnilube MB-11 Product of 49.35 9.90 192 32.0 28.5 Example 3 ReferenceExample 2 Example 4 Ethylether derivative of Product of 38.70 8.71 21463.0 66.5 monohydroxypolyoxypropyleneglycol Preparation Example 4Comparative Monohydroxypolyoxypropyleneglycol Material of 53.0 10.06 18055.5 57.5 Example 4 Preparation Example 4 Example 5 Ethyletherderivative of Product of 41.50 9.01 206 70.0 73.0dihydroxypolyoxypropyleneglycol Preparation Example 5 Example 6Ethylether derivative of Product of 40.76 8.10 177 73.0 74.5trihydroxypolyoxypropyleneglycol Preparation Example 6 Example 7Methylether derivative of Product of 32.0 7.50 214 79.5 80.5dihydroxypolyoxypropyleneglycol Preparation Example 7 Example 8Methylether derivative of Product of 47.56 9.70 195 70.5 70.5dihydroxypolyoxypropyleneglycol Preparation Example 8

PREPARATION EXAMPLE 9

In a 200-milliliter stainless steel autoclave equipped with a stirrerand a conduit, 3.0 g of powdery sodium methoxide was placed, sealed andheated at 105° C., and 100 g of propyleneoxide was introduced underpressure to the autoclave through a conduit over 9 hours, whilestirring.

After 100 ml of water and 200 mi of methanol were added and dissolved inthe reaction mixture, the solution was passed through a 200 ml column ofcation-exchange resin, then through a 200 ml column of anion-exchangeresin to remove sodium ion. After methanol and water were distilledaway, the residue was dried at 100° C. for an hour at a reduced pressure(0.4 mmhg) with a vacuum pump to obtain 96 g of the desiredpolyoxypropyleneglycol monomethylether.

PREPARATION EXAMPLE 10

In a 200-milliliter stainless steel autoclave equipped with a stirrerand a conduit, 1.6 g of methanol and 0.2 g of sodium hydroxide wereplaced, sealed, heated at 105° C. and 129.6 g of propyleneoxide wasintroduced under pressure to the autoclave through a conduit over 9hours.

After 100 ml of water and 200 ml of methanol were added and dissolved inthe reaction mixture, the solution was passed through a 200 ml column ofcation-exchange resin, then through a 200 ml column of anion-exchangeresin to remove sodium ion. After methanol and water were distilledaway, the residue was dried at 100° C. for one hour at a reducedpressure (0.4 mmHg) with a vacuum pump to obtain 115 g of the desiredpolyoxypropyleneglycol monomethylether.

PREPARATION EXAMPLE 11

The same procedure was repeated as in Preparation Example 1 except that4.42 g of sodium ethoxide was used in place of sodium methoxide and theamount of propyleneoxide was changed to 102 g to obtain 97 g of thedesired polyoxypropyleneglycol monoethylether.

EXAMPLE 9 TO 11 AND COMPARATIVE EXAMPLE 5

The compatibility with R-134a of the compounds obtained in PreparationExamples 9 to 11 and polyoxypropyleneglycol having a butyl ether groupat the one terminal and a hydroxyl group at the other terminal wasmeasured.

A specified sample was added into a pressure glass ampule so that theamount of the sample would be 10% by weight or 20% by weight to R-134a(1,1,1,2tetrafluoroethane), and this was jointed to a vacuum pipe andR-134a gas pipe. Afterwards, the ampule was subjected to vacuumdegassing at room temperature, and cooled with liquid nitrogen to takeout the specified R-134a. Then, the ampule was sealed, heated from −40°C. in a thermostat and starting temperature of phase separation wasmeasured. The results were shown in Table 2. The higher phase separationtemperature is preferable.

TABLE 2 Starting Temperature of Phase Separation (° C.) Ratio ofpolyglycol to 1,1,1,2-tetrafluoroethane Viscosity (cSt) Viscosity (wt %)No. Sample From 40° C. 100° C. Index 10% 20% Example 9Polyoxypropyleneglycol Product of 48.2 9.45 184 71.5 74.0monomethylether Preparation Example 9 Example 10 PolyoxypropyleneglycolProduct of 57.4 10.98 186 62.5 66.5 monomethylether Preparation Example10 Example 11 Polyoxypropyleneglycol Product of 62.13 11.70 187 58.060.0 monoethylether Preparation Example 11 ComparativePolyoxypropyleneglycol Unilube MB-11 56.1 10.8 187 51.5 54.0 Example 5mono-n-butylether Produced by Nippon Oil & Fats Co., Ltd.

EXAMPLE 12 TO 16 AND COMPARATIVE EXAMPLES 6 TO 9

For various kinds of polyoxyalkyleneglycol derivatives as sample oil,the starting temperature of phase separation (critical solutiontemperature) was determined according to the following test method.

In a 10 milliliter-glass autoclave, the sample oil and the refrigerant(R-134a) in a ratio of 1:9 (by weight) were placed and sealed, thengradually heated from the state of homogeneous solution, and thetemperature at which the sample oil and refrigerant began to separatewas measured as the critical solution temperature. The results are shownin Table 3.

TABLE 3 Kinematic Viscosity Polyoxyalkyleneglycol derivative of GeneralFormula (III) (cSt) Critical Solution No. R⁶ R⁷ p + q p / q 100° C.Temperature (° C.) Example 12 Methyl group Methyl group 40 1 24.0 49.0Comparative Methyl group Methyl group 40 0 22.4 19.5 Example 6Comparative Butyl group Hydrogen 36 1 25.7 32.0 Example 7 ComparativeButyl group Hydrogen 34 0 21.8 Separated Example 8 Example 13 Methylgroup Methyl group 20 1 9.50 74.0 Example 14 Methyl group Methyl group 61 2.86 90.0 or higher Example 15 Methyl group Hydrogen 32 1 21.9 41.0Comparative Methyl group Hydrogen 32 0 22.9 5.0 Example 9 Example 16Methyl group Hydrogen 22 1 9.45 73.0

As the above Table 3 shows, comparison of sample oils having similarvalues in kinematic viscosity shows that the sample oils in Exampleshave higher critical solution temperatures than those of sample oils ofthe Comparative Examples (Example 12 and Comparative Examples 6 to 8,Example 12 and Comparative Example 9, for instance).

EXAMPLES 17 TO 21 AND COMPARATIVE EXAMPLES 10 TO 24

Various kinds of polyoxyalkyleneglycol derivatives and the blends ofthem with various additives were used as sample oils, which weremeasured for critical solution temperature, stability, anti-wearproperty and anti-seizure property according to the following testmethods.

Kinematic viscosities of all sample oils were unified to about 11 cSt(100° C.).

(1) Critical Solution Temperature

In a glass autoclave with a capacity of about 10 ml, sample oil andrefrigerant (R-134a) were placed in the ratio of 1:9 (by weight) andsealed, then gradually heated up from the state of homogeneous solution.The temperature at which sample oil and refrigerant began to separatewas measured to be regarded as critical solution temperature.

(2) Stability

Evaluation was effected by Shield Tube Test.

A 2:1 mixture of the sample oil and the refrigerant (R-134a) was placed,together with a catalyst of iron, copper, or aluminum, in a glass tubeand sealed, and then heated at 175° C. for 720 hours. Then theappearance of the oil and the catalyst were observed, and the total acidnumber was determined.

(3) Anti-wear Property

Evaluation was performed by Falex Wear Test.

The amount worn was determined with the blowing amount of R-134a of 10liters/hour, load of 300 pounds, and a period of 1

(4) Anti-Seizure Property

Evaluation was made by Falex Seizure Test. According to ASTM D 3233,seizing load (pound) was determined with the blowing amount of R-134a of10 liters/hour. The results are in Table 4.

TABLE 4 Example Comparative Example 17 18 19 20 21 10 11 12 13 14Dihydroxypolyoxypropyleneglycol 99 — — — — — — — —Polyoxypropyleneglycol monomethylether — 99 — — — — — 99 99 99Polyoxypropyleneglycol dimethylether — — 99 — — — — — — —Ethyleneoxide-Propyleneoxide — — — 98 — — — — — — copolymerdimethylether Glycerolpropyleneoxide adduct — — — — 99 — — — — —Polyoxypropyleneglycol monobutylether — — — — — 99 — — — —Polyoxypropyleneglycol dibutylether — — — — — — 99 — — — Tricresylphosphate 1 1 1 2 1 1 1 — — — Dicresyl phosphate — — — — — — — 1 — —Trinonylphenyl phosphate — — — — — — — — 1 — Triphenyl phosphite — — — —— — — — — 1 Zinc Dithiophosphate — — — — — — — — — — Dioctyl sulfide — —— — — — — — — — Critical Solution Temperature (° C.) 67.5 67.5 66.5 67.567.5 58.5 52.5 67.5 Room 67.5 temperature (cloudy) Stability Appearance(Oil) Good Good Good Good Good Good Good Good not Good (Refrigerant:determined Flon 134a) Catalyst Good Good Good Good Good Good Good Goodnot Good determined Total Acid Number 0.1 or 0.1 or 0.1 or 0.1 or 0.1 or0.1 or 0.1 or 0.5 or not 0.5 or less less less less less less less moredetermined more Amount Worn (300 pounds × hr) (mg) 3 4 5 4 5 5 5 5 not 5determined Anti-Seizure Property (pounds) 800 800 800 800 800 800 800800 not 800 determined Comparative Example 15 16 17 18 19 20 21 22 23 24Dihydroxypolyoxypropyleneglycol — — — 100 — — — — —Polyoxypropyleneglycol monomethylether 99 99 — — 100 — — — — —Polyoxypropyleneglycol dimethylether — — — — — 100 — — — —Ethyleneoxide-Propyleneoxide — — — — — — 100 — — — copolymerdimethylether Glycerolpropyleneoxide adduct — — — — — — — 100 — —Polyoxypropyleneglycol monobutylether — — 99 — — — — — 100 —Polyoxypropyleneglycol dibutylether — — — — — — — — — 100 Tricresylphosphate — — — — — — — — — — Dicresyl phosphate — — 1 — — — — — — —Trinonylphenyl phosphate — — — — — — — — — — Triphenyl phosphite — — — —— — — — — — Zinc Dithiophosphate 1 — — — — — — — — — Dioctyl sulfide — 1— — — — — — — — Critical Solution Temperature (° C.) 67.5 67.5 58.5 67.067.0 67.0 67.0 66.5 57.5 52.0 Stability Appearance (Oil) colored coloredGood Good Good Good Good Good Good Good (Refrigerant: (yellow) (yellow)Flon 134a) Catalyst colored colored Good Good Good Good Good Good GoodGood (Fe) (Fe) Total Acid Number 0.5 or 0.1 or 0.5 or 0.1 or 0.1 or 0.1or 0.1 or 0.1 or 0.1 or 0.1 or more less more less less less less lessless less Amount Worn (300 pounds × hr) (mg) 7 7 5 5 5 5 5 5 5 5Anti-Seizure Property (pounds) 650 500 800 600 600 600 600 600 600 600

As is clear from the above Table 4, the sample oil of Examples arehigher in critical solution temperature and also superior inanti-seizure property, compared with Comparative Examples.

EXAMPLES 22 TO 24 AND COMPARATIVE EXAMPLES 27 TO 31

On the components shown in Table 5, critical solution temperature of thesolutions made by blending the sample oil and fluorine-containingrefrigerant R-134a in a ratio of 1:9 by weight. The result is shown inTable 5.

TABLE 5 Viscosity Critical Solution Temperature¹⁾ No. Component (40° C.)cSt low (° C.) high (° C.) Example 22 Glycerolpropyleneoxide adduct²⁾116 −50 or lower 80 (trifunctional group) Example 23Glycerolpropyleneoxide adduct³⁾ 96 −50 or lower 77 (trifunctional group)Example 24 Glycerolpropyleneoxide adduct⁴⁾ 103 −50 or lower 57(trifunctional group) Comparative Polypropyleneglycolmonobutylether⁵⁾105 −42 8 Example 27 (monofunctional group) ComparativePolypropyleneglycol⁶⁾ 150 −37 7 Example 28 (bifunctional group)Comparative Trimethylolpropanepropyleneoxide⁷⁾ 194 not dissolved¹⁰⁾ notdissolved¹⁰⁾ Example 29 adduct (trifunctional group) ComparativeSorbitol propyleneoxide adduct⁸⁾ 4275 not dissolved¹⁰⁾ not dissolved¹⁰⁾Example 30 (hexafunctional group) Comparative Glycerolpropyleneoxideadduct⁹⁾ 304 not dissolved¹⁰⁾ not dissolved¹⁰⁾ Example 31 (trifunctionalgroup) Notes: Water content of each sample oil of Examples andComparative Examples are all prepared to be 300 ppm. ¹⁾Test method ofCritical Solution Temperature In a glass pressure container with acapacity of about 10 ml, sample oil and refrigerant (R-134a) was placedin a ratio of 1:9, and sealed. The homogenous solution was cooledgradually on the lower temperature side, to find the temperature atwhich oil and refrigerant separated. On the higher temperature side, thesolution was gradually lowered in its temperature, and the temperatureat which the oil and refrigerant separated was found similarly. ²⁾SannixGP 400, produced by Sanyo Chemical Industries, Ltd. ³⁾Sannix GP 600,produced by Sanyo Chemical Industries, Ltd. ⁴⁾Sannix GP 1000, producedby Sanyo Chemical Industries, Ltd. ⁵⁾Unilube MB 19, produced by NipponOil & Fats Co., Ltd. ⁶⁾Sannix PP 2000, produced by Sanyo ChemicalIndustries, Ltd. ⁷⁾Sannix TP 400, produced by Sanyo Chemical Industries,Ltd- ⁸⁾Sannix SP 750, produced by Sanyo Chemical Industries, Ltd.⁹⁾Sannix GP 4000, produced by Sanyo Chemical Industries, Ltd.¹⁰⁾Insoluble with the refrigerant (R-134a) at ordinary temperature.

The components of Examples 22 to 24 are low in low-temperature criticalsolution temperature, and high in high-temperature critical solutiontemperature. It shows that at operation temperature, operation can befavorably effected without two-phase separation of refrigerant andrefrigerator oil.

EXAMPLES 25 TO 27 AND COMPARATIVE EXAMPLES 32 TO 34

6 g of a mixture of sample oil and R-134a in the ratio of 2:1 by weightwas placed in glass tubes together with iron wire, copper wire andaluminum wire each with a diameter of 1.5 Mm and a length of 40 Mm, andsealed. After maintained at 175° C. for 30 days and for 60 days, changesin the surface of each metal wire were observed by visual inspection.

No change was seen on the surface of copper or aluminum, but the surfaceof iron wire showed changes with some kinds of samples. The results ofthe observation of iron wire are shown in Table 6. It was confirmed thatthose having small water content showed no change.

TABLE 6 Shield Tube Test (Refrigerant: Flon 134a) 175° C. × 30 days 175°C. × 30 days No. Component Appearance of Iron Wire Appearance of IronWire Example 25 Glycerolpropyleneoxide adduct No change No change(trifunctional group) (slight decrease in luster) (decrease in luster)(Water content: 300 ppm) Example 26 Glycerolpropyleneoxide adduct¹⁾ Nochange No change (trifunctional group) (slight decrease in luster)(Water content: 150 ppm) Example 27 Glycerolpropyleneoxide adduct¹⁾ Nochange No change (trifunctional group) (Water content: 50 ppm)Comparative Glycerolpropyleneoxide adduct²⁾ No change Slight changeExample 32 (trifunctional group) (luster lost) (Water content: 1000 ppm)Comparative Glycerolpropyleneoxide adduct³⁾ Slight change discoloringExample 33 (trifunctional group) (Water content: 1%) ComparativeGlycerolpropyleneoxide adduct³⁾ discoloring discoloring Example 34(trifunctional group) (Water content: 5%) Notes: ¹⁾Example 27 wasdehydrated, to prepare a sample having water content of 50 and 150 ppm.²⁾Example 27 was let to stand for 30 hours in open state, to obtain asample having a water content of 1000 ppm. ³⁾Example 27 was added withwater, to prepare samples having a water content of 1% and 5% each,

EXAMPLES 28 TO 33 AND COMPARATIVE EXAMPLE 35

Refrigerator oils having the compositions shown in Table 7 wereprepared. Into a 10 milliliter-glass autoclave, said refrigerator oilswere each placed with R-134a as the refrigerant in a ratio of 1:9 byweight and sealed, then gradually heated up from the state ofhomogeneous solution. The temperature at which the oil and therefrigerant separate was measured to be regarded as critical solutiontemperature. The results are shown in Table 7.

TABLE 7 Composition of Refrigerator Oil (wt %) Component (a) Amount ofComponent (b) Critical Solution No. Kind* Amount (i) (ii) (iii) (iv)Temperature (° C.) Example 28 A-1 87 13 — — — 62.0 Example 29 A-1 76 —24 — — 64.0 Example 30 A-1 89 — — 11 — 57.5 Example 31 A-1 90 — — — 1059.0 Example 32 A-1 99.9 — 0.1 — — 53.5 Comparative A-1 100 — — — — 51.5Example 35 Example 33 A-2 80 — 20 — — 67.5 *A-1: Unilube MB 11(Polypropyleneglycol monobutylether, produced by Nippon Oil & Fats Co.,Ltd.) A-2: Sannix GP 1000 (Propyleneoxide adduct of glycerol, producedby Sanyo Chemical Industries, Ltd.) (i): Dioctyl adipate DOA (dibasicacid ester, produced by Mitsubishi Monsant Co., Ltd.) (ii): Daifloil 10(fluorinated oil, produced by Daikin Industries Co., Ltd.) (iii):Unistar H-306 (polyhydric alcohol ester, produced by Nippon Oil & FatsCo., Ltd.) (iv): LS-8210 (fluorosilicone, produced by Shin-etsu ChemicalIndustry)

EXAMPLES 34 TO 37

Various kinds of polyoxylalkylene glycol derivatives having formula(XIX) were used as sample oils, which were measured for criticalsolution temperature according to the following test methods.

In a glass autoclave with a capacity of about 10 ml, sample oils and arefrigerant (R-134a) were placed in a ratio of 1:9 (by weight) andsealed, then gradually heated up from the state of homogeneous solution.The temperature at which the sample oil and the refrigerant began toseparate was measured to be regarded as the critical solutiontemperature.

Load Resistance Test was performed according to ASTM 3233 by measuringthe seizing load (pound) after a test run for five minutes at an oiltemperature of 30° C. under a load of 150 pounds.

The result is shown in Table 8.

TABLE 8 Kinetic visc. at Critical Load Polypropyleneglycol 100° C.solution Resist- Example derivatives (cSt) temp. (° C.) ance Ex. 34Polypropyleneglycol 4.1 90 or more 630 monoallylether Ex. 35Polypropyleneglycol 9.2 66.0 735 monoallylether Ex. 36Polypropyleneglycol 3.4 84.0 540 monoallylether Ex. 37 Ethyleneoxide-5.2 86.0 640 propyleneoxide copolymer monoallylether Average numberAverage No. of alkylene oxide units molecular weight Example 34 7.6 500Example 35 14.5  900 Example 36 6.1 500 Example 37 4.3 & 4.3* 500*Numbers of EO units and PO units are 4.3, respectively.

In Table 8, “Critical solution temperature” means the phase separationtemperature of polyoxyalkyleneglycol derivative and R-134a. It will beobserved that the polyoxyalkyleneglycol derivatives in Examples 34 to 37have higher critical solution temperatures than those exhibited by theglycols shown in the Comparative Examples, thus these derivatives areshown to have excellent compatibility with R-134a.

EXAMPLES 38 TO 40

In the same manner as in Examples 1 to 8 additional experiments on thecompatibility of each sample of the polyoxyalkyleneglycol derivativehaving two alkyl terminal groups with R-134a were carried out. Theresults are shown in the following table.

TABLE 9 Kinetic Phase separation viscosity Temperature (° C.) Sample(cSt: 100°) (Concentration 10%) Remarks A 7.5 79.5 Example 7 B 9.1 74.0New Example 38 C 9.8 71.5 New Example 39 D 9.5 74.0 Example 13 E 9.070.0 Example 5 F 8.7 61.0 New Example 40 Average number Average No. ofalkylene oxide units molecular weight A 17.1 1040 B 19.6 1180 C 20.11210 D 9.1 & 9.1*  970 E — — F — — A: Methylether derivative ofdihydroxypolyoxypropyleneglycol Me—(PO)_(m)—Me B: Methylether derivativeof dihydroxypolyoxypropyleneglycol C: Methylether derivative ofdihydroxypolyoxypropyleneglycol D: Me—(PO)_(m)(EO)_(n)—Me, m:n = 1.1 E:Ethylether derivative of dihydroxypolyoxypropyleneglycol Et—(PO)_(m)—EtF: Ethylbutylether derivative of dihydroxypolyoxypropyleneglycol,Et—(PO)_(m)—Bu *Numbers of EO units and PO units are 9.1, respectively.

EXAMPLES 41 TO 44

Components (A), (B) and (C) shown below were used independently ormixed, to prepare refrigerator oils varying in ethylene oxide unit(C₂H₄O) content. These refrigerator oils as sample oils were evaluatedfor the properties as follows. The results are shown in Table 10.

(a) Antiwear property

According to Falex Wear Test, evaluation was made using aluminum blocks(A4032), and steel pins (SUJ-2). The amount worn was determined with ablow amount of R-134a of 10 liters/hour, a load of 300 pounds, and aperiod of 1 hour.

(b) Suitability to sealing materials (in according with JIS K6301)

High nitrile rubber was used as the sealing material, and the ratio ofchange in volume at 130° C. after 72 hours was measured.

(c) Peeling property of coating material

The refrigerator oil was dropped onto the outer wall of the receivertank of a refrigerator coated with synthetic resin, left for 24 hours,and then the oil drops were wiped out with thin cotton cloth. At thatwiping, it was observed whether the coating was peeled off or not.

(d) Compatibility with Refrigerant (Phase Separation Temperature)

Into a glass autoclave with a capacity of about 10 ml, sample oil andrefrigerant (R-134a or R-12) are placed in homogeneous solution weregradually heated to find a temperature at which the sample oil and therefrigerant began to separate, which was regarded as the phaseseparation temperature.

TABLE 10 Properties Composition Suitability (C₂H₄O) Antiwear to SealingPeeling Content Property Antiwear of Coating Phase Separation (° C.)Component (wt %) (mg) (%)*1 Material R-134a R-12 Example 40 Mixture of 3 20 or less 16.8 No 70 or more 70 or more Compounds A and B Example 41Mixture of 10 20 or less 17.0 No 70 or more 70 or more Compounds A and BExample 42 Mixture of 20 20 or less 17.9 No 70 or more 70 or moreCompounds A and B Example 43 Compound C 10 20 or less 17.5 No 70 or more70 or more only Example 44 Compound C 20 20 or less 18.0 No 70 or more70 or more only Compound A: CH₃O(C₃H₆O)_(m)CH₃ (Kinematic Viscosity at100° C.: 9.1 cSt) Compound B: CH₃O(C₂H₄O)_(x)(C₃H₆O)_(y)CH₃ x = y = 9.1(Content of C₂H₄O Unit: 41%) Compound C: CH₃O(C₂H₄O)_(x)(C₃H₆O)_(y)CH₃Content of C₂H₄O unit was adjusted as per the Table. *1: Ratio of changein Volume

What is claimed is:
 1. A method for effecting lubrication incompression-type refrigerators using 1,1,1,2-tetrafluoroethane as arefrigerant which comprises employing, as a lubricant, a lubricating oilcomprising, as a main component, a polyoxyalkyleneglycol derivative ofethyleneoxide-propyleneoxide copolymer represented by the generalformula: R⁶—O—A—R⁷ or the general formula: [CH₂—O—A—R⁸ CH—O—A—R⁹CH₂—O—A—R¹⁰]

wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each an alkyl group having 1 to 3carbon atoms, A is a copolymerization chain of ethyleneoxide andpropyleneoxide, consisting of p-times ethyleneoxide units and q-timespropyleneoxide units and p and q are numbers satisfying therequirements: 0.1≦p/q≦10, 5≦p+q≦100.
 2. A method according to claim 1wherein all of R⁶ to R¹⁰ are methyl groups.
 3. A compression-typerefrigerator system which comprises a compressor, a refrigerantcomprising 1,1,1,2-tetrafluoroethane, and a lubricant, said lubricantcomprising a lubricating oil which comprises, as a main component, apolyoxyalkyleneglycol derivative of ethyleneoxide-propyleneoxidecopolymer represented by the general formula: R⁶—O—A—R⁷ or the generalformula:

wherein R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each an alkyl group having 1 to 3carbon atoms, A is a copolymerization chain of ethyleneoxide andpropyleneoxide consisting of p-times ethyleneoxide units and q-timespropyleneoxide units and p and q are numbers satisfying therequirements: 0.1≦p/q≦10, 5≦p+q≦100.
 4. A compression-type refrigeratorsystem according to claim 3, wherein all of R⁶ to R¹⁰ are methyl groups.